scholarly journals Spatiotemporal Variability of Surface Phytoplankton Carbon and Carbon-to-Chlorophyll a Ratio in the South China Sea Based on Satellite Data

2020 ◽  
Vol 13 (1) ◽  
pp. 30
Author(s):  
Wenlong Xu ◽  
Guifen Wang ◽  
Long Jiang ◽  
Xuhua Cheng ◽  
Wen Zhou ◽  
...  
Keyword(s):  
South China Sea ◽  
Chlorophyll A ◽  
South China ◽  
Satellite Data ◽  
Phytoplankton Biomass ◽  
The South China Sea ◽  
Spatiotemporal Variability ◽  
The South ◽  
Chl A ◽  
China Sea

The spatiotemporal variability of phytoplankton biomass has been widely studied because of its importance in biogeochemical cycles. Chlorophyll a (Chl-a)—an essential pigment present in photoautotrophic organisms—is widely used as an indicator for oceanic phytoplankton biomass because it could be easily measured with calibrated optical sensors. However, the intracellular Chl-a content varies with light, nutrient levels, and temperature and could misrepresent phytoplankton biomass. In this study, we estimated the concentration of phytoplankton carbon—a more suitable indicator for phytoplankton biomass—using a regionally adjusted bio-optical algorithm with satellite data in the South China Sea (SCS). Phytoplankton carbon and the carbon-to-Chl-a ratio (θ) exhibited considerable variability spatially and seasonally. Generally, phytoplankton carbon in the northern SCS was higher than that in the western and central parts. The regional monthly mean phytoplankton carbon in the northern SCS showed a prominent peak during December and January. A similar pattern was shown in the central part of SCS, but its peak was weaker. Besides the winter peak, the western part of SCS had a secondary maximum of phytoplankton carbon during summer. θ exhibited significant seasonal variability in the northern SCS, but a relatively weak seasonal change in the western and central parts. θ had a peak in September and a trough in January in the northern and central parts of SCS, whereas in the western SCS the minimum and maximum θ was found in August and during October–April of the following year, respectively. Overall, θ ranged from 26.06 to 123.99 in the SCS, which implies that the carbon content could vary up to four times given a specific Chl-a value. The variations in θ were found to be related to changing phytoplankton community composition, as well as dynamic phytoplankton physiological activities in response to environmental influences; which also exhibit much spatial differences in the SCS. Our results imply that the spatiotemporal variability of θ should be considered, rather than simply used a single value when converting Chl-a to phytoplankton carbon biomass in the SCS, especially, when verifying the simulation results of biogeochemical models.

scholarly journals Research on Cold Core Eddy Change and Phytoplankton Bloom Induced by Typhoons: Case Studies in the South China Sea

2015 ◽  
Vol 2015 ◽  
pp. 1-19 ◽  
Author(s):  
Xiao-dong Shang ◽  
Hai-bin Zhu ◽  
Gui-ying Chen ◽  
Chi Xu ◽  
Qi Yang
Keyword(s):  
South China Sea ◽  
South China ◽  
Mechanical Energy ◽  
The South China Sea ◽  
Gravitational Potential Energy ◽  
The South ◽  
Chl A ◽  
China Sea ◽  
Slow Transit ◽  
Transit Speed

The effects of 8 typhoons which passed by coldcore eddy (CCE) areas in the South China Sea (SCS) from 1997 to 2009 were observed and evaluated. The changes in the preexisting CCE acted upon by typhoons were described by eddy kinetic energy (EKE) and eddy available gravitational potential energy (EAGPE). The mechanical energy of CCE was estimated from a two-layer reduced gravity model. Comparing with the scenario that typhoon passes by the region without CCEs, the preexisting CCE area plays an important role in the increase of chlorophyll-a (chl-a) concentration in the CCEs impacted by the typhoons. The preexisting chl-a in CCE is about 25%~45% (8%~25%) of postexisting chl-a in CCE for higher (slower) transit speed typhoons. If the EAGPE of CCE increases greatly after typhoon passing by with slow transit speed, so does the chl-a in the CCE area. The EKE (EAGPE) changes of the preexisting CCE are in the order of O(1014~1015 J). EKE and EAGPE of CCE are dominantly enhanced by typhoon with slow transit speed (<3 m/s) and the posttyphoon EAGPE is always larger than posttyphoon EKE for 8 cases. The maximum EAGPE change of the preexisting CCE reaches5.11×1015 J, which was induced by typhoon Hagibis.

scholarly journals The variability of chlorophyll-a and its relationship with dynamic factors in the basin of the South China Sea

2019 ◽  
Vol 200 ◽  
pp. 103230 ◽  
Author(s):  
Yi Yu ◽  
Xiaogang Xing ◽  
Hailong Liu ◽  
Yeping Yuan ◽  
Yuntao Wang ◽  
...  
Keyword(s):  
South China Sea ◽  
Chlorophyll A ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea ◽  
Dynamic Factors

scholarly journals Satellite data lift the veil on offshore platforms in the South China Sea

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Yongxue Liu ◽  
Chao Sun ◽  
Jiaqi Sun ◽  
Hongyi Li ◽  
Wenfeng Zhan ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Satellite Data ◽  
The South China Sea ◽  
Offshore Platforms ◽  
The South ◽  
China Sea ◽  
The Veil

scholarly journals The Effect of the ENSO on the Variability of SST and Chlorophyll-a in the South China Sea

2019 ◽  
Vol 246 ◽  
pp. 012027 ◽  
Author(s):  
Siti Maisyarah ◽  
Anindya Wirasatriya ◽  
Jarot Marwoto ◽  
Petrus Subardjo ◽  
Indra B Prasetyawan
Keyword(s):  
South China Sea ◽  
Chlorophyll A ◽  
South China ◽  
The South China Sea ◽  
The South ◽  
China Sea

scholarly journals Behaviour of Dissolved Phosphorus with the associated nutrients in relation to phytoplankton biomass of the Rajang River-South China Sea continuum

2019 ◽  
Author(s):  
Edwin Sien Aun Sia ◽  
Jing Zhang ◽  
Shan Jiang ◽  
Zhuoyi Zhu ◽  
Gonzalo Carrasco ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Phytoplankton Biomass ◽  
Salinity Gradient ◽  
The South China Sea ◽  
Organic Nitrate ◽  
Nutrient Loads ◽  
The South ◽  
Wet Season ◽  
China Sea

Abstract. Nutrient loads carried by large rivers and discharged into the continental shelf and coastal waters are vital to support primary production. Our knowledge of tropical river systems is still fragmented with very few seasonal studies available for Southeast Asia for example, despite estimates that these systems are among the hotspots globally for nutrient yields. The Rajang river, the longest river in Malaysia, is a tropical peat-draining river which passes through peat-domes in the estuary and has mass discharge of organic matter into the South China Sea. Three sampling campaigns (August 2016, March 2017 and September 2017) were undertaken along ~ 300 km of the Rajang river to study both spatial and seasonal distribution of nutrients and its fate in the coastal region. The analyses for nutrients encompass both inorganic (i.e Nitrate, NO3−, Nitrite, NO2−, Ammonium, NH4+, Phosphate, PO4− (DIP) and Silicate, dSi) as well as organic (Dissolved organic nitrate, DON and Dissolved organic phosphate, DOP) fractions. It was found that DIP concentration was not seasonally influenced but was spatially different along the salinity gradient whereas DOP was both seasonally and spatially different. Both DIP and DOP exhibited non-conservative behaviour in the mixing. DIP was subjected to 57.78 % removal whereas DOP was subjected to 44.07 % addition along the salinity gradient towards the South China Sea. The bulk of the dissolved phosphate is from DOP (73.84 %), in which both DIP and DOP may have contributed to the phytoplankton biomass. Spearman’s correlations show that there was a switch in preference for DOP as compared to DIP depending on the concentrations of DIP or DOP due to seasonality. The main limitation in the Rajang River was assumed to be DIP based on the Redfield ratio. During the dry season, the NO3-N : DIP ratios were lower, which were ideal conditions for phytoplankton proliferation while in the wet season, the increased NO3-N : DIP ratios led to lower phytoplankton biomass. Overall, the Rajang River exports 0.12 t DIP mth−1 into the South China Sea which is relatively low as compared to other major peat-draining rivers in the world. At the current pace of deforestation and the projected intensification of rainfall in the region, this finding provides an important baseline of the inventory of DIP into the South China Sea. Our results also show that local variations are important to consider for future models and that the assumption/generalization of SEA as a nutrient hotspot might not hold true for all regions and requires further investigations.

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